Computer network

Computer network is a system consisting of computers and other network devices that work together to achieve a common goal.

The purpose of the computer network are:
• Sharing the resources: for example, shared use of printers, CPUs, memory, hard drive
• Communication: eg electronic mail, instant messaging, chat
• Access to information: for example web browsing
In order to achieve the same goal, each part of the computer network and provide service request (service). Party requesting the service is called a client (client) and that provide services called the servant (the server). This architecture is called client-server systems, and is used in almost all computer network applications.

Classification Based on the scale:
• Personal Area Network (PAN)
• Campus Area Network (CAN)
• Local Area Network (LAN): a computer network that connects a computer to another computer with a limited distance.
• Metropolitant Area Network (MAN): principle the same as LAN, only the larger distance, ie 10-50 km.
• Wide Area Network (WAN): the distance between cities, countries, and continents. This is the same with the Internet.
• Global Area Network (GAN)

Based on the function: Basically every computer network is functioning as a client and server. But there is a network that has a dedicated computer as a server and the other as a client. There is also a computer that has no special function as a server only. Therefore, based on their function there are two types of computer networks:


• Client-server
Network is the computer with a dedicated computer as a server. A service / service can be provided by a computer or more. An example is a domain like www.detik.com lots served by the web server computer. Or it could be a lot of service / services provided by a single computer. Examples are jtk.polban.ac.id server that is a multi-service computer with the mail servers, web servers, file servers, database servers and others.

• Peer-to-peer
Namely computer networks where each host can be a server and also a client simultaneously. For example in the file sharing between computers on the Windows Network Neighborhood Network have 5 computers (we give the name of A, B, C, D and E) that provide access rights to the files they have. At one point A to access the file share of B named data_nilai.xls and also gives access to the file soal_uas.doc C. When accessing a file from B then A serves as a client and as a give file access to C then A serves as a server. Both functions were performed by the same A network like this is called peer to peer.

Based on network topology, computer networks can be divided into:
• bus topology
• star topology
• ring topology
• mesh topology
• Topology tree
• Linear topology

Based on the criteria, the computer network can be divided into 4, namely:
1. Based on the distribution of sources of information / data
- This network centralized network consisting of Client and server computers which Client computer that serves as an intermediary to access sources of information / data derived from a single server computer
- Network is a combination of several distributed centralized network so that there are several computer servers that are interconnected with the Client to form a specific network system.

2. Based on geographic coverage can be divided into:
- Network LAN is a network that connects 2 computers or more in coverage such as laboratories, offices, and in 1 cafe.
- MAN network is a network that includes a big city and its local area. Examples of local telephone networks, cellular telephone systems, as well as some ISPs relay network Internet.
- Network WAN is a network with coverage throughout the world. PT network example. Telkom, PT. Indosat, as well as GSM networks such as Cellular Satelindo, Telkomsel, and much more.

3. Based on the roles and relationships of each computer in the data processing.
- Network Client-Server In this network there are 1 or more server computers and client computers. Computers will be computers or servers to client computers and altered through the protocol software on the network. Client computer as an intermediary to be able to access data on a server computer and the server computer to provide information needed by the client computer.
-Network Peer-to-peer in this network there are no client computer or server computer because all computers can make sending and receiving information so that all computers function as clients as well as a server.

4. Based on the data transmission media
- Wired Network (Wired Network) In this network, to connect one computer to another computer in the form of necessary liaison network cable. Function in the network cable to send information in the form of electrical signals between the network computer.

- Wireless Network (Wireless Network) is a network with the medium of electromagnetic waves. In this network does not need a cable to connect between computers that use electromagnetic waves to send signals between the computer information network